Two pole transducer



Oct. 6, 1964 J. A. Ross 3,152,270

TWO POLE TRANSDUCER Filed March 21, 1960 4 Sheets-Sheet 1 INVENTOR.

JAMES A. ROSS AGENT 1964 J. A. Ross 3,152,270

TWO POLE TRANSDUCER Filed March 21, 1960 4 Sheets-Sheet 2 FIG. 3.

FIGQ9.

INVENTOR. JAMES A. ROSS AGENT Oct. 6, 1964 J. A. Ross 3,152,270

TWO POLE TRANSDUCER Filed March 21, 1960 4 Sheetshe 3 FIG. 7.

FIG. 8. 5s;

INVENTOR. JAMES A. ROSS AGENT Oct. 6, 1964 J. A. Ross 3,152,270

TWO POLE TRANSDUCER Filed March 21. 1960 4 sheets sheet 4 FIG. IO.

FIG. II.

FIG. l2. I

I6I e2 [{AMPLIFIER" DE LAY 7o 94 I56 I5I T 95 I62 83 as AMPLIFIER DELAYI 96 I57 I52 T 91 i I63 84 gngAMPLlFlER DELAY I58 I53 T 99 I AMPLIFIERDELAY 85 E IOO I5 I54 T MPLIFIER DELAY 9| I A I02 I60 I55 T I 3INVENTOR.

JAMES A. ROSS AGENT United States Patent 3,152,270 TWO POLE TRANSDUCERJames A. Ross, Orange, Califi, assignor to Ling-Temco- Vought, Inc.,Dallas, Tex a corporation of Delaware Filed Mar. 21, 1960, Ser. No.16,429 28 Claims. (Cl. 310-47) My invention relates to an electrical tomechanical transducer and particularly to such transducers having a flatconductive plate-like armature and a field structure to pass magneticflux transversely through said plate.

The armature of the well-known electrodynamic loudspeaker type ofelectromechanical transducer consists of a circular coil of wire, a formto support the same and spider-like means to mechanically connect theform to a useful load.

I have previously invented a four pole transducer, which is described inmy application for United States patent Serial No. 749,539, filed July18, 1958, now Patent No. 2,944,194, issued July 5, 1960. In this fourpole transducer the armature is in the form of a piece of crossshapedelectrically conductive metal with four magnetic poles laterallyadjacent to the arms of the cross.

This application is concerned with a new and highly simplified form oftransducer in which the armature is effectively a fiat plate and onlytwo magnetic poles are required to provide a suitable flux pattern forthe armature. Not only is this an important simplification, but the newstructure provides convenient structural advantages.

Briefly, these advantages embrace a field structure in which the fluxdensity at the air-gap is the same as in the remainder of the magneticstructure, an alternate type of field structure in which connections tothe armature are easily made, and a shape of armature that isparticularly adapted for driving loads supported on a slip table. By wayof comparison, the flux density at the airgap in my four pole transduceris only 70% of the maximum flux density in the field structure of thatdevice. The maximum density occurs at the throat between pairs of polepieces. The throat is required in the four pole transducer to provideroom for the four pole armature.

Alternate embodiments provide a particularly simple field structure andlaminated armature structures for either sonic phase drive or relativelyhigh electrical input impedance to the transducer.

An object of my invention is to provide an electromechanical transducerhaving an armature of great simplicity.

Another object is to provide an electromechanical transducer having anefilcient field structure.

Another object is to provide a field structure that allows convenientexternal connections for the armature of an electromechanicaltransducer.

Another object is to provide an armature that is particularlymechanically suited to drive a specimen upon a vibration slip table.

Another object is to provide a unified connection scheme for botharmature and shading conductors in an electromechanical transducer.

Another object is to provide an armature of simple structural shape butof relatively high electrical input impedance.

Another object is to provide a structure for an electromechanicaltransducer that is simple, of relatively light Weight and which hasrugged principal parts.

Other objects will become apparent upon reading the following detailedspecification and upon examining the accompanying drawings, in which areset forth by way of illustration and example certain embodiments of myinvention.

3,152,270 Patented Get. 6, 1964 PEG. 1 shows an end perspective view ofthe essential structure of my transducer,

FIG. 2 shows a horizontal section along lines 2-2 in FIG. 1, showing themanner in which external connections are made in one form of armature,

FIG. 3 shows an end elevation view of an alternate embodiment of myinvention in which a particularly simple field structure is employed,

FIG. 4 shows a side elevation of a structure in which the plate-likearmature of my invention is employed with a slip table,

FIG. 5 shows principally a plan view of a sectionalized armature,

FIG. 6 shows an end view of the armature of FIG. 5 in combination withadjacent shading conductors,

FIG. 7 shows a side sectional elevation of a sectionalized armature andassociated structure,

FIG. 8 shows a wiring diagram for the armature and associated structureof FIG. 7,

FIG. 9 shows an alternate form of the transducer of FIG. 4,

FIG. 10 shows a curved armature embodiment similar to FIG. 3,

FIG. ll shows a curved armature embodiment similar to FIG. 4, and

FIG. 12 shows connections for delayed armature feed according to FIGS. 5and 6.

In FIG. 1 numeral 1 indicates the iron field structure. This has theapproximate shape of tangent double cylinders with a common central slotWithin which armature 2 fits. At least two field coils 3 and 4individually surround the toroid-like iron structure on opposite sidesof the center of the assembly. These coils pass through central holes ineach cylinder as well as encompassing the outer surface and the two endsurfaces.

Normally, a constant current of a number of amperes is passed throughboth coils 3 and 4 in the proper direction to produce a mutually aidingmagnetic field in the structure as a whole. One magnetic pole is formedabove the central slot, as indicated at N, and the opposite pole isformed below the slot, as indicated at S. The magnetornotive force thusprovided normally saturates the field structure, at a flux density ofthe order of 100,000 lines per square inch.

It will be seen that relatively uniform magnetic flux thus passes acrossthe slot perpendicularly to the plane or" the flat armature 2.Electrical connections are provided at the narrow sides of the armatureand an alternating current is caused to flow through the armature platein FIG. 1 from left to right, and vice versa according to the electricalalternations. This causes motion of the armature up and down through theplane of the paper (the motor rule).

Although the magnetic and electrodynamic aspects of the structure ofFIG. 1 are symetrical with respect to armature 2, the auxiliary aspectsare not. These have to do with passing the current into and out of theannature; i.e., the connections. Broadly, these pass to the externalcircuit at one side; the right side in FIGS. 1 and 2.

Stationary shading conductors or sheets are provided on the pole facesof the field structure to reduce the inductance of the armature system.In the present instance these are placing on both sides of the slot inthe field structure, and in FIG. 1 are identified as 5 on the upper poleand 6 on the lower. These sheets are insulated from the field structure,are mechanically a part of it and are coextensive with the armature.

The excitation circuit of the transducer of FIGS. 1 and 2 consists ofarmature 2 in series with shading sheets 5 and 6 in parallel. Theexcitation circuit is connected to power input means, such asimpedance-reducing transformer 7. In detail, a copper strap secondary a;of transformer 7 connects to a number of flexible high-conductivityarmature connection straps 9, lil, ll, l2, l3, 34. A nut-bolt assembly15' is shown as accomplishing this juncture. Large and clean surfaces ofcontact should be arranged, since the impedance of the whole excitationcircuit is only a small fraction of an ohm. Alternately, the contact maybe formed by brazing or welding.

The armature connection straps pass through slots in the field structureI in order to reach the armature proper. The respective slots and theelectrical insulation provided on all the faces thereof are identifiedin FIG. 2 as 1.6, 17, l3, 19, 2t 21. In a relatively high powerembodiment of my invention in which the length of field structure 1might be two feet, the open area of each slot is of the order of severalinches in depth by a fraction of an inch in width. The correspondingstraps are smaller so that some mechanical motion is possible within theslots. The chief mechanical fiexure, however, occurs to the left of theslots and to the right of the armature proper in FIG. 2. In this volumethe straps branch out so that exciting current is relatively uniformlydistributed over the fiat armature. An excess in strap length isprovided to accommodate the necessary vibration of the armature, thedirection of which is indicated by the two-headed arrow 22. The centralstraps, as 18, 19 and perhaps 17 and 2%, have a further excess length toequalize the resistance be tween the several straps. This is alsocarried out in practice adjacent to the bolt connection 15, but has notbeen shown in FIG. 2 for sake of clarity.

Alternately, the straps 9 through 14 are a tight fit in the fieldstructure by narrowing slots 16 through ill. The cross-section of ironin the field structure is main tained approximately constant byproviding proiections 2d and 25.

Armature connection straps 9 through 14 are arranged to make a lowresistance electrical connection with armature 2 by brazing, silversoldering, welding, etc., by passing into tight-fitting slots thereinand then bonded. Six straps are shown; more or fewer may be used. Topstrap 9 appears in FIG. 1.

On the left side of armature 2 connection is made the two shading sheets5 and d by curving one piece of high conductivity metal, as copper, intoa semicircle at 27 in FIG. 2, so that sheets 5, 6, and end connection 27are all one. At 2'7, a number of flexible straps 28, 29, 36, 31, 32, 33connect from armature 2 to end connection 27. The number, material andfastening may be the same as discussed for the right-hand armatureconnections 9 through 1 An alternate left-hand connection is shown inFIG. 1. A connection bar 35 is provided, to which the several flexibleconnections 23, etc. are fastened. In turn, two sheetllliG connections36, 3'7 connect the length of the bar to shading sheets 5, 6, so thatthe electrical scheme of connections is as before.

In a manner similar to that described, electrical connection is madebetween the right-hand ends of shading sheets 5, 6. These connectionsare arranged out of mechanical conflict with the armature connectionstraps 9 through 14-, as straps 39, dd; front and back with respects tothe armature straps in the plan view of FIG. 2 to cross over the shadingsheet connections from one side to the other of the main field structureslot. On each end of the slot straps 59, 4h curve toward the center toconnect the whole ends of the shading sheets (FIG. 2).

External connection 41 connects with connection 39 and becomes one withsecondary 8 of transformer 7. An additional connection to the same endof secondary 8 may also be taken but has not been shown since it isoptional.

Primary 44 of transformer '7 has considerably higher impedance thansecondary The ratio is normally from a small fraction of an ohm forsecondary 8 to several ohms for primary 44 This primary is thenconnected to the low impedance secondary of the output transformer ofthe high power audio amplifier employed to drive this transducer and theprimary of the output transformer is connected to the plates of thevacuum tubes as known.

In case a low impedance driving source is available, as themulti-rectifier device of the High Power Synthetic Waveform Generator ofRoss and Harter, patent application No. 850,595, filed November 3, 1959,one transformer 7 is sufi'icient to accomplish the necessary impedanceconversion.

An alternate embodiment of my invention is shown in FIG. 3, wherein atoroid of iron 51 has a single air-gap along a radius. The central holeof the toroid allows a field winding 54 to encircle the same and toprovide a magnetic flux as before when current is passed through thefield winding. Armature 52 has the structural form of a flat conductiveplate and is centered in the gap in the field structure, all as before.The armature may be composed of many laminations as will be laterdescribed but the structural form is the same.

Only one field coil is required and has been shown. More can be addedaround the toroid if desired for practical reasons. One magnetic pole,say a north pole N is formed on the upper pole face and the oppositepole, S, on the lower pole face. Shading sheet 55 is insulatinglyattached to the stationary N pole and shading sheet .56 is similarlyattached to the lower S pole.

Because the left-hand edge of armature 52 is not confined by the fieldstructure almost any arrangement of electrical connections to thearmature can be had. The first of a series of flexible strips 59 isshown. Others of the same nature as 28, 2%, etc. in FIG. 2 are behindstrip 59. These each attach to both the armature and a stationaryconnection bus 60. The latter, in turn, is connected to one end of a lowimpedance secondary 58 of transformer 57. The shading sheets 55 and 56extend beyond the field structure to the left and connect to the otherend of secondary 58. An additional low imped ancc secondary 68 oftransformer 57 is connected in parallel to secondary 58. This alternateconstruction allows smaller conductors to be employed than as shown at 8in FIG. 2. A higher impedance primary 61 completes transformer 5'7 andthis primary is connected to electrical enervy exciting means as hasbeen previously described.

At the right-hand side of armature 52 shading sheets 55 and 56 areformed together in a curved portion (53 and a series of flexiblearmature connections are connected thereto, of which connection is atthe front and so is seen.

In either the embodiment of FIG. 1 or 3 the armature is retained inslidable relation to the stationary portion of the structure by means ofhigh pressure oil. A known oil pump suited to provide oil pressure, agear type proportional flow divider and suitable pipes meter an equalamount of oil to each pole face N and S. Through holes drilled in thefield structures relatively perpendicular to the pole faces, as at 42,43 in FIG. 1 and at 66, 67 in FIG. 3, the oil flows from the pipingsystem to substantially the center of each pole face.

The oil is distributed over the whole face of the shading sheet, by, forexample, a spiral groove cut outwardly from the central hole. Anoticeable separation has been shown between the armature and theshading sheets in the figures herein for sake of clarity but thisdistance is only a few thousandths of an inch in practice. The equalizedoil pressure holds the armature centered in the field gap in each caseand provides a cushion of lubrication upon which the armature slideswhen it is supplied with actuating current. A thin transformer oilhaving an S.A.E. equivalent of five is employed, an example of which isShell Dyala oil.

While I do not restrict the application of my invention, orientation ofthe structure so that armature plate 2 lies in a horizontal plane hascertain advantages. Re-

storing springs are not required. This results in simplicity andimproved fidelity of vibration over the more common orientation of thearmature in the vertical position.

As a practical matter, two or more weak springs may be employed atconvenient points, as the corners of the armature, to insure that itremains well centered. However, this function can be taken over by theseveral electrical connecting straps 9 through lid and 28 through 33 byproviding these with spring-like properties. Should it be desired tooperate the transducer with the armature vertical, suitable leaf springsmay be provided as shown and described in my prior four-pole transducerpatent.

Typical horizontal operation of the armature is shown in FIG. 4. Here acommon baseplate 7th acts as the overall base of the machine. It may beprovided with casters for mobility. A field structure 71 of thembodiment of FIG. 3 is seen in side elevation. Armature 72 extends inone piece from within the field structure, as in FIG. 3, to completelyover a black granite block '73. An oil film between the granite blockand the extended portion of the armature 72 allows vibration of thearmature to take place under the load of specimen 75. The latter isbolted or clamped directly to armature 72 and a vibrating system ofideal simplicity results. If the specimen is to be vibrated in anotherplane it is merely bolted to the armature in another position. A portionof the field excitation winding '74 is seen at the left in FIG. 4.

It is obvious from this construction that the vibrationally complicatedstructure of the prior art including moving coil, spider and specificwork table is eliminated. Consequently, so are turning moments and thepossibility of parasitic vibrations. My simple moving system is suitedto follow the waveform of the incoming alternating current withfidelity.

Armature 72 may be made of a single piece of aluminum, aluminum alloy orberyllium, or the armatures of FIGS. 1, 2 or 3 may be extended byarranging studs in tapped holes 46 or fittings on bosses 126 in FIG. 7.

FIG. 5 shows an electrically sectionalized armature provided to bedriven in vibrational phase at high frequencies and FIG. 6 shows howthis armature coacts with its immediately adjacent shading conductor andfield structures. Should the armature of FIG. 5 (a plan view) be of theorder of 20 inches long, this length corresponds to a quarter-wavelengthin aluminum for an audio frequency of 3,000 cycles. A quarter-Wavelengthis the distance from a node to a loop of vibratory wave energy. Thus,the phase of vibratory response dilfers conditionally along the lengthof the armature for high frequencies of this order. This results indecreased efficiency at high frequencies for large transducers of thesiZe required in vibration practice. In FIG. 5 the armature iselectrically segmentized. Each segment is fed with electrical energyappropriately phased so that the electromagnetic driving force and thevibratory response are in phase throughout the length of the armature.

Accordingly, in the example of FIG. 5 successive segments 82, 83, 84,85, 86 are of equal length and width and divide the length of thearmature into five equal sections. Each of these is fed separatelyelectrically, as from flexible connections 87, 38, 89, 90, 91. Theseconnections continue to the external electrical circuits throughseparately insulated conductors in a common bus bar assemblage 92.

The armature is fabricated mechanically as a prestressed structure bytensioned wires 106, shown in FIGS. 5 and 6. A tension of the order of120,000 pounds per square inch is produced in the Wires. This creates acompressive stress in the segmented aluminum armature of the order of10,000 pounds per square inch. The maximum stress created by vibrationof the armature in use is of the order of 5,000 pounds per square inch,so the armature is always a rigid structure. In practice perhaps 32wires 6 each one-fourth inch in diameter are used of piano wirematerial. Only six such wires have been shown in FIG. 5 for sake ofclarity. Natural mica, or other insulation suited to high compressivestress, separates the laminations at 105 for necessary electricalinsulation.

In FIG. 5 only armature input connections 857 through 91 have been shownfor sake of simplicity, but the armature circuit is completed throughanother set of connections in the manner of either of FIG. 2 or 3. Eachpair of connections conveys actuating electrical energy to an armaturesegment at a different electrical phase. The phase delivered to armaturesection 86 may be considered zero or reference phase. Since there arefive sections in the armature illustrated that phase of electricalenergy impressed upon the next section is delayed by external meansone-fifth of ninety electrical degrees l8 electrical degrees, at 3,000cycles. This is 17 microseconds in time. Such a delay is provided by adelay line or by equivalent means in an amplifier feeding this sectionof the armature. In a similar manner the electrical energy fed to eachsucceeding section 84, 83, 82 is delayed 17 microseconds more than theenergy feeding each prior section. This technique is understandable fromthe explanation immediately above; however, details on the externalequipment are given in my previously mentioned patent on the four poletransducer.

In the embodiment of FIGS. 5 and 6 the prior shading sheets becomeshading sections. There is at least one shading section for eacharmature section. These shading sections are shown at 94 through 103 inFIG. 6. These are insulated, one from the other, and from the fieldstructure 51, to which they are structurally attached.

Connections for the delayed armature feed are given in FIG. 12. Thearmature sections 82-86 follow FIG. 5 and the shading sections 94-103follow FIG. 6. Each corresponding group is fed by a separatetransformer, as 161 to 165. The initial source of alternating currentvibratory energy is connected to terminal 150. Successive delay elements151-155, such as known delay lines, give successively equal incrementsof delay to each feed. Amplifiers 156-160 are normally individual poweramplifiers each having sufficient output power to energize one out ofthe groups of armature-shading assemblies shown.

In any of FIGS. 1, 2, 3, 6 alternate arrangements besides thoseillustrated may be employed for connecting the armature to the shadingelements and these to the external circuits. In FIG. 3, for example,flexible armature connecting strips 64- may be directly andindependently (as a group) connected to the left side of transformersecondary 58. The shading sheets are connected back upon themselves.That is, connection 63 is retained and a similar connection is made atthe left ends of sheets 55 and 56. This arrangement may becharacter-ized as the direct armature connection to the electri caldriving means.

As a further alternate the shading sheets, only, may be connected to thedriving means and the armature is driven by induction. In this, thearmature connections 59, 64 are connected back on themselves external tothe magnetic field and shading sheet connection 63 isconnected to theright-hand side of secondary 58 at 60. With the shading sheet feed theimpedance is higher than when the armature is fed alone.

Further considering FIGS. 5 and 6 structurally, elements 107 representtension adjusting fitments. There are nuts screwed upon the threadedends of wires 106 and supplied with insulating washers underneath. Eachsegment of the armature, 82 through 86, must be electrically insulated,one from the other so that the phasing can be accomplished. Each wire isprovided with insulation 93 throughout its length and the holes in theseveral sections of the armature are large enough to accommodate thisinsulation. The insulation may be provided by dipping each wire in ahigh quality rubber and then curing the same so that the rubber isbonded to the wire. Suitable it hollow cylindrical tubing of insulatingmaterial may also be employed.

In FIG. 7 there is shown a further embodiment of my invention, followingthe structure of FIG. 6 in a general way. This structure has anelectrical impedance much higher than that of the embodiments that havebeen described.

Numerals Ilt'i, 111, 112 identify characteristic armature laminations, arelatively large number of which are employed, say from 30 to 160 inspecific practical applications. These are normally fabricated fromaluminum or aluminum alloy. Insulation is provided between eachlamination, as at 113, I14, 115. This should be natural mica or anotherinsulator capable of withstanding compressive stress without yielding. Anumber of tensioned steel strips 116 are employed to bind thelaminations into a unified structure. These partake of the generalnature of the wires 106 of FIG. but usually half as many are employed asin the case of wires, such as 16 strips 1" wide by 0.1" thick. In FIG. 7the strips 116 are aligned one behind the other and so only the one atthe section can be seen. As with the wires the strips are highlystressed so as to bind the armature into a rigid body under allconditions of vibration.

A tail end plate 117 has the same general shape of a lamination but agreater thickness. Each strip 116 has two hook lugs 118 which fit intosuitable notches in tail end plate 117. When a rectangular hole in eachlamination and the plate 117 for each strip 116 it will be seen how therigid body is assembled. Each strip is insulated from each of thelaminations by a rubber substance 119 coated on each strip after initialfabrication of the strip. The insulation between laminations, i.e. 113,114, 115 may have a somewhat smaller rectangular hole than is in thelaminations per se and thus each lamination insulator centers the stripaway from the metallic laminations.

A head end plate 125 completes the armature structure at the right sideof FIG. 7. This has a greater than lamination thickness, as did theopposite tail end plate, but is provided with a round hole in additionto the rectangular slot for each strip. A threaded stud 124 is securelyfastened to the top of each strip after the pile of laminations isassembled and then head end plate 125 is attached. A boss 126 is thenscrewed upon each stud and tightened to provide the tension desired. Theboss itself is provided with a slot and central hole so that thespecimen to be vibrated or an additional slip table slab can beattached.

The several elements identified by numeral 125) are shading conductors.In the center of the vibratory excursion of the armature (from left toright and vice versa in FIG. 7) each shading conductor is aligned withan armature lamination. These are identified as 131. The armature isshown in its center-of-excursion position in FIG. 7. Immediatelyopposite to laminations 131 are the shading conductors on the oppositepole face, each identified as 121. While only a group of each of thesealigned elements have been identified by the numerals it will beunderstood that each corresponding element of the whole stack issimilarly identified.

Each shading conductor is insulated from every other shading conductorand from the pole face to which it is attached in assembly. This isaccomplished by a rubber and fiber-glass bonding particularly betweenthe shading conductors and the pole face. Each shading conductor isspaced a few thousandths of an inch from the ones adjacent to it and atleast some of the bonding material fills this space and so sets eachshading conductor in an insulating suround. The bonding material isindicated at 122 on upper pole face 123 and at 123 on lower pole face129. Upper face 123 corresponds to the N pole of FIG. 3 and the lowerface to the S pole. In this embodiment it will be seen that the head andtail end plates and the tensioned strips are electrically one, but

this is of no moment because electrical connections of the armaturecircuit are not made thereto. This arrangement has the advantage ofproviding a simple and rugged mechanical structure.

The gap between armature and stationary shading conductors is also onlyof the order of onehundredth of an inch in this embodiment and oil underpressure is preferably used as a suspending medium. In addition,however, I employ a thin sheet of insulation bonded to the armature,either over a restricted area adjacent to the head and tail end platesor over the whole lateral surface of both sides of the armature. Thismay be Teflon or an equivalent substance and is identified in FIG. 7 as127. This prevents electrical damage in case of failure of the oilpressure.

FIG. 8 shows how the vibration energizing alternatcurrent is connectedto the armature-shading conductor assembly. Only four groups of armaturelaminations and corresponding top and bottom shading conductors areshown but it Will be understood that the scheme of connection shownembraces all of this assembly.

The scheme of connection is a series one, with each armature laminationconnected in series with the two shading conductors associated with itin parallel; those shading conductors connected to the next armaturelamination, and so on.

Each group of lamination and shading conductors is shown in perspectiveso that the connections may be more clearly shown. Each armaturelamination is iden tified as 131, each upper shading conductor as 12!)and each lower shading conductor as 1.1; corresponding to theidentification in FIG. 7.

An output transformer 1.33 connects between the plate output of a highpower audio frequency power amplitier as known in vibration techniquesand my transducer. It has approximately the characteristics of the usualsuch output transformer. The impedance of secondary 135 may be afraction of an ohm and the impedance of primary 13d of the order of onethousand ohms. The special strap conductor secondary of FIG. 2 is notrequireu.

One external circuit connection 136 connects between one side ofsecondary 135 and the first, or right-hand armature lamination 131. Asindicated by the arrow, the instantaneous direction of the current isfrom back to front of this lamination. Reaching the front the currentdivides to go to each of the associated shading conductors 126, top, and121, bottom. Flexible connections 137 and 133, respectively, establishthese conne tions. The current then flows through both of the shadingconductors in a direction opposite to the flow through the armaturelamination, as will be noted by the arrows. When this traverse has beencompleted the currents are joined by flexible connections 139 and 140and connected to the second armature lamination. Here the fiow from backto front agains occurs, flexible connections again halve the current andpass it to both shading conductors in which it flows back and thenthrough further flexible connections to the next armature lamination,and so on.

After passing through the whole armature-shading assembly the current isjoined from the last two shading conductors by stationary connection141. This, in turn, connects to the opposite side of transformersecondary 135 through connection 142.

Because of this relatively extensive series circuit it will berecognized that the impedance of this assembly is many times greaterthan the impedance of a solid armature such as in FIG. 2. The structuresof FIGS. 7 and 8 are not phased, however, but the construction isemployed to obtain a higher impedance than otherwise and so do withoutvery low impedance transformer 7 of FIG. 2.

Still further alternate embodiments are possible.

When the active part of the armature 72 of FIG. 4 is laminated accordingto FIG. 7, as has been described,

an additional laminated part can be added at the right hand side of FIG.4, along with a coacting additional field structure 71. This makes adouble-ended transducer that is very effective for high power work. Thevibrating structure is particularly simple and thus suited for highperformance. This alternate embodiment is shown in FIG. 9.

A permanent magnet field element may be employed at 1, 51 or 71 insteadof the electromagnet shown. While the toroid shape for the fieldstructure is preferred, this can be of a hollow square shape for FIG. 3and of a double E shape in FIG. 1.

The fiat plate armatures shown throughout this specification areparticularly suited for fastening directly to a specimen or to the slipplate of a slip table. However, a further plate can be bolted to studholes 46 in FIGS. 1 through 6 or fastened to bosses 12s of FIG. 7,particularly if any of these transducers are to be operated verticallyrather than horizontally.

Also, the thus far considered flat plate shape for the armaturestructures can be made curved, as the arc of a circle. In FIG. 2 or 5,for example, the center of the armature is depressed and the right andleft sides are raised above the plane of the paper. The gap in the fieldstructure is correspondingly curved, as an arc replacing the planaraspects of 2 in FIG. 1. In this manner structural strength at extremelightness can be achieved because of the stiffening of the armature.

These constructions are shown in FIGS. and 11; the former referring toFIG. 3 by reference numerals found therein and provided with primes inFIG. 10, the latter referring to FIG. 4 and similarly identified. Theequivalent structure may be employed in FIG. 2 or 5, as has beenexplained.

In any of the several embodiments it will be appreciated that the flowof oil adjacent to the armature acts to cool it, and the adjacentshading structure.

My novel armature may be characterized as a vane, Whether planar orshaped in a curved surface and whether solid or segmented.

While relatively large and high power transducers have been illustratedand described, my transducer is suitable for miniaturization by merelyscaling down all sizes. Other physical modifications may be made in thearrangement, proportions and combinations of the several embodimentsgiven. Other electrical modifications may be made in the characteristicsof the circuit elements, the coactive relation between such elements anddetails of circuit connection without departing from my invention.

Having thus fully described my invention and the manner in which it isto be practiced, I claim:

1. An electromechanical transducer comprising only one electricallyconductive vane,

means to impress a magnetic field transversely through the thickness ofall of said vane,

and plural flexible connection means to pass an electric current acrosssaid vane for motional excitation thereof.

2. An electrical to mechanical transducer comprising only one segmentedconductive plate,

means to impress a magnetic field transversely through the thickness ofall of said plate,

and means to pass an electric current through the segments of said plateat right angles to said magnetic field for motional excitation of saidplate.

3. An electromechanical transducer comprising only one flat electricallyconductive horizontally disposed armature having two lateral surfaces,

means to impress a uniform magnetic field perpendicularly throughsubstantially all of the area of said lateral surfaces of said armature,

and multiple flexible connection means to pass an alternating current inthe direction of a major di- 1h mension of said armature for themotional excitation thereof.

4. An electromechanical transducer comprising only one electricallyconductive vane of non-magnetic material,

a laterally disposed magnetic structure coextensive with said vane andhaving a pole facing each side of said vane,

plural groups of external conductors, each said group having pluralconductors connected to an edge of said vane and to an external sourceof current to mechanically move said vane,

and fluid means under said vane to position said vane in relation tosaid magnetic field structure to allow motion of said vane relative tosaid magnetic field structure.

5. An electro-dynamic shaker comprising only one transverselyelectrically conductive plate-like armature having greater conductivityin one direction than in another,

a magnetic field structure having one pole face directly abutting eachside of said armature,

an electrical conductor mounted on at least one said pole face,

external conductors connecting one edge of said armature to an adjacentend of said electrical conductor,

further external conductors connecting another edge of said armature andanother end of said electrical conductor to an external source ofelectric current to energize said armature,

and liquid means to laterally position said armature within said fieldstructure for the free vibration of said armature.

6. An electrical to mechanical transducer comprising only oneelectrically conductive flat armature,

a stationary magnetic field structure having one pole face directlyabutting each lateral surface of said armature,

at least one insulated shading conductor for reducing inductance mountedon each said pole face adjacent to said armature,

external conductors connecting one edge of said armature to the adjacentends of said shading conductors,

further external conductors connecting the opposite edge of saidarmature and the opposite ends of said shading conductors to an externalsource of alternating current to vibrate said armature,

and liquid pressure means to laterally position said armature withinsaid field structure for the free vibration of said armaturetransversely with respect to the magnetic field impressed upon saidarmature by said magnetic field structure.

7. An electromechanical shaker comprising a conductive vane armature,

a bi-toroidal field structure having a central gap to completely enclosesaid armature,

at least one coil upon a toroid of said field structure to produce amagnetic field across said central gap disposed with the plane of saidcoil angularly removed from the direction of maximum dimension of saidarmature,

openings in a field toroid adjacent to said armature,

connectors attached to said armature and passing through said openingsto external electrical circuit means for energizing said armature,

a conductor attached to each side of said gap in said field structureadjacent to said armature,

connections from each of said conductors to said armature,

and connectors attached to said conductors adjacent to said openings andpassing from said field toroid at the ends of the central hole thereofto said external electrical circuit means.

8. An electrical to mechanical transducer comprising an electricallyconductive pirate-shaped armature of non-magnetic material,

a bi-toroidal field structure having a common central gap to completelylaterally enclose said armature,

a toroidal coil surrounding each toroid of said field structure toproduce a magnetic field therein,

the plane of at least one said toroidal coil angularly removed from theplane of said armature,

ducts in the plane of said armature in that field toriod having saidcoil angularly removed,

flexible connectors attached to an edge of said armature and passinghrough said ducts to external electrical circuit means for energizingsaid armature,

a shading conductive sheet insulatingly attached to each side of saidcentral gap of said field structure adjacent said armature,

electrical connections from each of said sheets to the edge of saidarmature opposite said prior edge,

connectors attached to the ends of said shading sheets adjacent to saidducts and passing from the field toroid at the ends of the centralaperture thereof to said external electrical circuit means,

holes in said bi-toroidal field structure through said shading sheets,

and means to force fluid under pressure through said holes to supportsaid armature for movement with respect to said field structure.

9. An electromechanical transducer comprising only one vane-likearmature,

a circular magnetic field structure having a radial opening tomechanically accommodate the minimum dimension of said armature,

means to produce a magnetic field across opening,

a conductor upon each pole face of said opening adjacent to saidarmature,

a fiexible connection between said conductor and said armature at thesmallest radius of said circular field structure,

a transformer Winding,

flexible connections between said transformer winding and said armatureat the largest radius of said field structure,

and another connection between said transformer winding and saidconductors to complete an electrical circuit for the excitation of saidarmature.

10. The transducer of claim 9 in which said vane-like armature has theform of a curved surface in one dimension and the direction of saidmagnetic field and the location of said flexible connections are such asto cause motion in a dimension perpendicular to that of said curvedsurface.

11. An electrical to mechanical transducer comprising an electricallyconductive fiat plate-like armature,

a toroidal magnetic field structure having one radial gap to accommodatesaid armature,

a field coil toroidally wound around said field structure to magnetizethe same,

an insulated shading conductor upon each pole face of said gap closelyadjacent to said armature,

flexible connections between said shading conductor and the edge of saidarmature at the smallest radius of said toroidal field structure,

a low impedance transformer winding,

flexible connections between one terminal of said transformer windingand the edge of said armature at the largest radius of said toroidalfield structure,

a connection between the other terminal of said transformer winding andsaid shading conductors on each said pole face,

and fluid pressure means to position said armature within the gap insaid field structure for the free motion of said armature with respectto said field upon both said armature and said field being energizedwith electric current.

said

12. The transducer of claim 11 in which two low impedance windings ofsaid transformer are connected in parallel to said armature and saidshading conductors.

13. An electromechanical vibrative device comprising a magnetic fieldstructure having pole pieces,

an electrically conductive armature having the shape of a small segmentof a cylindrical surface disposed between and extending beyond said polepieces,

a member of large inertia supporting said extended part of saidarmature,

flexible means connected to said armature for passing current throughthe same,

and means upon said extended part to fasten a specimen to said armature.

14-. An electrical to mechanical transducer comprising a magnetic fieldstructure having a single horizontally disposed planar gap,

a single electrically-conductive non-magnetic flat platelike armaturedisposed within said gap and extending beyond it in one direction,

flexible connection means connected to said armature for passingelectric current through that portion of said armature disposed withinsaid gap,

a member of large inertia supporting the extended portion of saidarmature,

a lubricant between said member and said armature,

a common base for said field structure and said member,

and means upon the extended part of said armature to attach a specimento be vibrated directly to said armature.

15. An electrical to mechanical transducer comprising two spacedmagnetic field structures each having a single horizontally disposedgap,

an electrically conductive flat plate armature extending between saidfield structures and disposed within said gap of each,

electrical connection means connected between said armature and astationary source of electric current,

and one member of large inertia supporting said armature.

16. The transducer of claim 15 in which the parts of said armaturedisposed within said gaps are laminated transversely of the length ofsaid armature.

17. The transducer of claim 15 in which the parts of said armaturedisposed within said gaps are laminated, stationary shading conductorsare aligned with said laminations and the laminated parts of saidarmature are electrically interconnected with adjacent said shadingconductors for the vibrational excitation of said armature.

18. In an electromechanical transducer having an elongated fiat armatureand a field structure for impressing a magnetic field transverselythrough said armature, means for establishing electrical connection tosaid armature through said field structure compromising pluralconductors disposed along said armature and plural slots in said fieldstructure for passing said conductors through said field structure, saidfield structure formed of increased external size adjacent to said slotsto maintain the cross-section of said field structure substantially thesame as the cross-section away from said slots.

19. In an electromechanical transducer having an armature and a singleslot field structure for impressing a magnetic field transverselythrough said armature, means for establishing electrical connection tosaid armature comprising plural flexible strip conductors disposed alongsaid armature, plural slots in said field structure for passing saidconductors through said field structure, and insulation lining each saidslot to insulate said conductors from said field structure.

20. The connection means of claim 19 in which said armature issectionalized and each said flexible strip connects one section thereofto separate phase-related circuits.

21. The connection means of claim 19 in which each said flexible stripis comprised of plural conductive ribbons and the depth of saidinsulated slots is such as to clamp the ribbon strips Within said slots.

22. In an electromechanical transducer having a planar armature and afield structure for impressing a magnetic field transversely throughsaid planar armature, means for establishing external electricalconnection to said planar armature comprising a plurality of flexiblestrip conductors disposed along an edge of said plate, the sameplurality of said slots in said field structure adjacent to saidconductors for passing said conductors through said field structure toexternal electrical connections, there being one said conductor in eachone said slot, and insulation lining each said slot to insulate saidconductors from said field structure.

23. An electromechanical device comprising a plurality of elongatedconductive armature sections disposed in an aligned stack plural membersin tension insulatingly disposed within said armature to hold saidsections together, field pole faces laterally adjacent to said armature,magnetomotive force means to pass magnetic flux through said pole facesand through said armature,

the same plurality of conductor sections fastened to said pole faces inalignment with said armature sections,

means to electrically connect each group of said aligned armaturesections and each corresponding said conductor section,

means to pass electric current through at least one of said armature andsaid conductor sections in each said group,

a connection from each said means to each corresponding said armatureeach conductor section,

and means to delay the electric current through each said armature andconductor section corresponding to the time for propagation of amechanical Wave along said stacked armature.

24. An electrical to mechanical transducer comprising a plurality ofseparately-insulated conductive armature sections stacked in astructurally unified plate-like assembly,

one field pole face adjacent to each side of said armature stack,

means to form magnetic poles of opposite polarity on opposite said fieldpole faces,

the same plurality of separately-insulated shading sections attached tosaid pole faces in lateral alignment with said armature sections andclosely adjacent thereto,

said armature sections electrically connected to each said shadingsection having the same relative position as the particular armaturesection,

the same plurality of means to pass an electric current through saidarmature and said shading sections,

one connection from each said means to each corresponding said armatureand shading section,

and means to delay in time the electric current through each saidarmature and shading section corresponding to the time for propagationof a mechanical impulse along said stacked armature.

25. An electrical to mechanical transducer comprising a plurality ofseparately-insulated conductive armature sections disposed in acongruent stack,

insulated tensioned elements attached thereto to compress said stack,

pole faces adjacent to each side of said armature stack,

means to form magnetic poles of opposite polarity on opposite sides ofsaid armature stack,

the same plurality of separately-insulated shading sections attached toeach said pole face in alignment with said armature sections and closelyadjacent thereto,

each said armature section electrically connected to each said shadingsection having the same relative position as the said armature section,

and means to pass an electric current through all said armature and saidshading sections.

26. An electromechanical transducer comprising a plurality of stackedseparately-insulated non-magnetic conductive armature segments eachhaving plural aligned central apertures,

a strip of high tensile strength material passing through an alignedaperture in each said segment.

means to insulate each said strip from each said aperture,

plates to compress said stacked segments,

means to exert a tension upon each said strip greater than any tensioninduced in said strip by mechanical stress of the transducing process tocompress said stacked segments by means of said plates,

means to pass a magnetic field through each of said armature segments,

the same plurality of separately-insulated stationary shading conductorsdisposed adjacent to said armature segments,

means to successively electrically connect each said armature segment toadjacent said shading conductors,

and further means to connect the first of said armature segments and thelast of said shading conductors to an energizing electrical circuit.

27. An electromechanical transducer comprising plural separateconductive armature segments,

tensioned members attached to said segments to form a rigid vane-likearmature structure,

means to pass a magnetic field through each of said armature segments,

the same plurality of insulated shading conductors disposed adjacent tosaid armature segments on each side thereof and attached to said meansto pass a magnetic field,

means to electrically energize said armature for vibration,

conductive means to connect one end of the first of said plural armaturesegments to said means-to-energize,

conductive means to connect the opposite end of said first armaturesegment to one end of each of the first of said shading conductors,

conductive means to connect the opposite ends of each of said firstshading conductors to one end of the second of said armature segments,

conductive means to connect the other end of said second armaturesegment to one end of each of the second of said shading conductors,

and further said conductive means to connect successive said pluralityof armature segments and corresponding pairs of said plurality ofshading conductors,

and final conductive means to connect the last of said pairs of shadingconductors to said means-to-energize to complete the electrical circuit,

28. An electrical to mechanical transducer comprising a large pluralityof separately-insulated non-magnetic linear conductive armature segmentshaving aligned apertures,

strips of high tensile strength material passing through said alignedapertures,

means to insulate each said strip from each said aperture,

means to exert a tension upon each said strip greater than any tensioncaused in said strip by the mechanical eifect of the transducingprocess,

means to pass a magnetic field through each of said armature segmentsperpendicular to the alignment of said apertures,

the same plurality of separately-insulated shading conductors disposedadjacent to said armature segments on each side thereof upon said meansto pass a magnetic field,

alternating-current means to electrically energize said armature forvibration,

flexible means to connect one end of the first of said plural armaturesegments to said alternating-current means,

flexible means to connect the opposite end of said first armaturesegment to one end of each of the first said shading conductors,

flexible means to connect the opposite ends of each of said firstshading conductors to one end of the second of said armature segments,

flexible means to connect the other end of said second armature segmentto one end of each of the second of said shading conductors,

and further said flexible means to connect said plurality of armaturesegments and corresponding pairs of said plurality of shadingconductors,

final conductive means to connect the last of said pairs of shadingconductors to said alternating-current means to complete a serieselectrical circuit,

and fluid pressure means to position said armature for motion withrespect to said shading conductors.

References Cited in the file of this patent UNITED STATES PATENTS Re.24,816 Woods Apr. 26, 1960 1,266,988 Pridham May 21, 1918 1,589,019Purser June 15, 1926 1,672,351 Thomas June 5, 1928 1,682,866 ThomasSept. 4, 1928 2,053,619 Le Golf Sept. 8, 1936 2,134,510 Hague Oct. 25,1938 3,004,180 Macks Oct. 10, 1961

1. AN ELECTROMECHANICAL TRANSDUCER COMPRISING ONLY ONE ELECTRICALLYCONDUCTIVE VANE, MEANS TO IMPRESS A MAGNETIC FIELD TRANSVERSELY THROUGHTHE THICKNESS OF ALL OF SAID VANE, AND PLURAL FLEXIBLE CONNECTION MEANSTO PASS AN ELECTRIC CURRENT ACROSS SAID VANE FOR MOTIONAL EXCITATIONTHEREOF.